<!DOCTYPE html>
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<title>Cssl.html</title>
	<style type="text/css">
	
		/* 交集选择器 */
		h3.color_yellow{
			color:yellow;
		}
	</style>
</head>
<body>
	<h3>我是一个h3啊</h3>
	<h3>我是一个h3啊</h3>
	<h3 class="color_yellow">我是一个h3啊</h3>
</body>
</html>
